Why is My Positive Battery Terminal Hot

If you’ve ever noticed that your positive battery terminal is hot, it can be a cause for concern. The battery terminal is an essential component of your vehicle’s electrical system, and understanding why it gets hot can help you identify and address potential issues. In this article, we will explore the reasons behind a hot positive battery terminal and provide insights on what steps you can take to resolve the problem.


Corrosion is a common issue that can cause your positive battery terminal to become hot. When battery terminals corrode, the flow of electricity can become restricted, resulting in resistance and heat build-up. This resistance occurs due to the chemical reaction between battery acid and the terminal metal. Over time, corrosion can increase the resistance and cause additional heat to be generated in the terminal.

To address corrosion-related heat, you can follow these steps:

  • Disconnect the negative terminal first to avoid any electrical shock.
  • Inspect the positive terminal for signs of corrosion, such as a powdery substance or greenish buildup.
  • Clean the terminal using a battery terminal cleaner or a mixture of baking soda and water.
  • Gently scrub the terminal with a wire brush or terminal cleaning tool to remove any corrosion.
  • Apply a thin layer of petroleum jelly or anti-corrosion spray to the terminal to prevent future corrosion.

Loose Connections

Another reason for a hot positive battery terminal is loose connections. When the terminal connections are not properly tightened, it can lead to increased resistance and heat generation. Over time, the heat can become significant enough to cause the terminal to feel hot to the touch.

To address loose connections and prevent the terminal from becoming hot, follow these steps:

  1. Disconnect the negative terminal to ensure safety.
  2. Inspect the positive terminal and cable for any signs of looseness.
  3. If the connections are loose, use a wrench or socket set to tighten them securely.
  4. Ensure that there is no movement or play in the terminal or cable after tightening.


In some cases, an overcharging alternator can lead to a hot positive battery terminal. The alternator is responsible for replenishing the battery’s charge while the engine is running. However, if the alternator malfunctions and delivers too much voltage, it can cause excessive charging and result in a hot battery terminal.

If you suspect overcharging as the cause, you can check the charging system by following these steps:

  1. Start the engine and allow it to run for a few minutes.
  2. Using a multimeter, set it to DC voltage and connect the positive and negative leads to the corresponding battery terminals.
  3. Observe the voltage reading on the multimeter. It should be within the range specified by your vehicle’s manufacturer.
  4. If the voltage reading is too high or fluctuating, it indicates a problem with the charging system, and you should have it inspected by a professional.

Faulty Battery

Occasionally, a faulty or failing battery can cause the positive terminal to become hot. Internal issues within the battery, such as short circuits or improper chemical reactions, can lead to increased resistance and excessive heat generation at the terminal.

If you suspect a faulty battery, it is important to have it tested by a professional. They can perform load tests and other diagnostic procedures to identify any issues with the battery. If necessary, they can recommend a replacement battery to resolve the heat problem.

High Electrical Load

A high electrical load on your vehicle’s electrical system can also contribute to a hot positive battery terminal. This can occur when multiple accessories or systems are drawing power simultaneously, placing a heavier demand on the battery and its terminal. Examples of high electrical load situations include using power-hungry devices like stereos, lights, or high-wattage speakers.

If you frequently experience a hot positive battery terminal due to high electrical load, you can take the following measures:

  • Reduce the use of power-hungry accessories or devices, especially when the engine is not running.
  • Consider upgrading your battery or alternator to handle a higher electrical load if necessary.

In conclusion, a hot positive battery terminal can be caused by various factors such as corrosion, loose connections, overcharging, a faulty battery, or high electrical load. By understanding these potential causes and following the suggested steps to address them, you can ensure a safer and more reliable electrical system in your vehicle.